1. Field of the Invention
The present invention generally relates to an internal combustion engine control apparatus configured to estimate an intake air quantity drawn into a cylinder of an engine. More specifically, the present invention relates to an internal combustion engine control apparatus configured to estimate an actual cylinder intake air quantity in a simple manner in an engine configured to control a cylinder intake air quantity by varying the valve timing of intake valves.
2. Background Information
Conventional gasoline engines are provided with a throttle valve for controlling the intake air quantity, and the amount of air that passes through the throttle valve is measured with an airflow meter provided upstream of the throttle valve. In such conventional engines, the measured amount of air that passed through the throttle valve is generally used as a load indicator, which is used as a parameter for controlling the engine. For example, Japanese Laid-Open Patent Publication No. 2002-256938 discloses a conventional internal combustion engine control apparatus in which an intake air quantity of an internal combustion engine (a gasoline engine) is controlled using a throttle valve to achieve a target torque. In the above mentioned reference, the quantity of intake air that passes through the throttle valve is estimated and the estimated intake air quantity is used as a load indicator for setting the target torque.
In other type of conventional engines, the amount of air that flows into the cylinder (hereinafter called “cylinder intake air quantity”) is measured instead of the amount of air that passes through the throttle valve so that the cylinder intake air quantity is used as a load indicator. For example, Japanese Laid-Open Patent Publication No. 2001-050091 discloses this type of conventional engine that is configured to calculate the amount of air that flows into the intake manifold based on the output of an airflow meter, and to calculate the cylinder intake air quantity and the amount of air inside the intake manifold based on the difference between the detected amount of air that flows into the intake manifold and an amount of air (the cylinder intake air quantity) that flows from the intake manifold into the cylinder.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved internal combustion engine control apparatus. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.